Multiport nozzle for retract starting



March 1, 1966 INVENTORS ROBERT M. GAGE 25 WILLIAM F? KEANE United States Patent 3,238,348 MULTIPORT NOZZLE FOR RETRAtIT STARTING Robert M. Gage, Summit, and William P. Keane, Arlington, N.J., assignors to Union Carbide Corporation, a corporation of New York Filed Aug. 27, 1963, Ser. No. 305,001 2 Claims. (Cl. 219-75) This invention relates to multiport nozzles for retract starting of arc working processes.

In such processes an electric arc is drawn between two electrodes, and a stream of gas is introduced into the arc zone and forms an arc plasma which is directed toward the workpiece through a centrally located passage in a gas directing nozzle which gives stability to the arc plasma effluent.

This invention constitutes an improvement upon the disclosure of the co-pending application of Leonard Mauskapf, Serial No. 183,871, filed March 30, 1962, in which another flow of gas is directed along and outside of the arc plasma issuing from the centrally located passage, to increase the speed of operation and improve the quality of the product. To direct this other flow, a multiport nozzle is provided, having a plurality of holes surrounding the central constricting passageway.

This Mauskapf multiport nozzle is applicable to the retract starting torch of the type shown in the co-pending application of J. S. Kane and P. R. Schaefer, Serial No. 292,552, filed July 3, 1963. In starting the operation, the electrode is lowered into contact with the inside of the multiport nozzle, and then retracted to start the arc. Repetition of such retract starting causes material such as copper from the electrode carrier or the inside of the nozzle to flake off. Such flakes tend to clog the smaller holes in the multiport nozzle.

The main object of the present invention is to prevent or decrease the clogging of such smaller holes in a multiport nozzle of this character.

According to the invention, the smaller holes in the multiport nozzle are made of greater diameter at their inner ends than at their outer ends. Preferably such greater diameter is provided by counterboring the inner ends of the smaller holes from the inside of the nozzle.

In the drawings:

FIGURE 1 is a vertical section through a retract starting Plasmarc torch provided with a nozzle embodying the preferred embodiment of the present invention; and

3,238,348 Patented Mar. 1, 1966 FIGURE 2 is a transverse section line 22 of FIG. 1.

The retract starting Plasmarc torch comprises a front body 19 and a rear body (not shown) in which an electrode 12 is slidably mounted. The upper portion of the electrode 12 is axially bored to receive a hollow rod 14, the lower portion of which forms a water baffle tube 16.

The lower end of the electrode is surrounded by a gasdirecting nozzle 18 having an upper annular flange fitting the front body 10. A ceramic insulator 20 is interposed between the electrode 12 and the front body 10. A hollow cap 22 is screwed onto the outside of the front body to secure the nozzle 18 thereon.

The nozzle 18 comprises a cup having a central inverted frusto-conical socket 24. The bottom of the cup has a central constrictive passageway 23 surrounded by a plurality of holes 25. The holes 25 are preferably drilled from the outside up into the socket 24, and are preferably from eight to sixteen in number and preferably equidistantly spaced from, and considerably smaller than, the constrictive orifice 23. The holes 25 are preferably sufficiently close to each other to form gas streams which merge and form a substantially annular gas stream surrounding the effluent plasma from the constrictive passageway 23.

The holes 25 are preferably of greater diameter at their inner than at their outer ends. For this purpose, the holes 25 are counterbored at their inner ends as at 29, to prevent or decrease clogging of the holes by flakes formed by arcing the electrode 12 and the socket 24.

What is claimed is:

1. In a plasma arc torch comprising an electrode, a gas-directing nozzle having a constricted passageway below said electrode and a plurality of gas ports surrounding said passageway, said electrode being retractable away from the inside of said nozzle to start the arc, the improvement which comprises the inner ends of said ports being of greater diameter than the outer ends thereof.

2. Multiport nozzle for a plasma arc torch as claimed in claim 1, in which the inner ends of said plurality of gas ports are counterbored to said larger diameter.

References Cited by the Examiner UNITED STATES PATENTS 2,887,562 5/1959 Mencotti 2l975 3,148,263 9/1964 Jensen 2l975 RICHARD M. WOOD, Primary Examiner.

taken along the 

1. IN A PLASMA ARC TORCH COMPRISING AN ELECTRODE, A GAS-DIRECTING NOZZLE HAVING A CONSTRICTED PASSAGEWAY BELOW SAID ELECTRODE AND A PLURALITY OF GAS PORTS SURROUNDING SAID PASSAGEWAY, SAID ELECTRODE BEING RETRACHABLE AWAY FROM THE INSIDE OF SAID NOZZLE TO START THE ARC, THE IMPROVEMENT WHICH COMPRISES THE INNER ENDS OF SAID PORTS BEING OF GREATER DIAMETER THAN THE OUTER ENDS THEREOF. 